The present invention relates to an exposure method and apparatus therefor, an exposure system and a mask circuit pattern inspection system, which eliminate an influence of interference light generated in an extremely fine circuit pattern formed on a mask, so that an image is formed with a high resolving power on a substrate through a projection lens and exposed and, further, wherein the light source is an excimer laser light source.
In the manufacture of an LSI, a circuit pattern on a mask is exposed and transferred onto a wafer to form a fine circuit pattern on the wafer. However, to cope with the need of high integration of LSI, the circuit pattern transferred onto the wafer tends to be an extremely fine pattern, which constitutes a resolution limit of an imaging optical system.
In view of the foregoing, various techniques have been developed in order to transfer an extremely fine circuit pattern.
For example, there is a method for exposure using X-rays such as SOR (Synchrotron Organized Resonance) light. There is a further method which uses an EB (Electron Beam) exposure machine. Furthermore, there is another method using an excimer laser disclosed in "Excimer Laser Stepper for Sub-half Micron Lithography, Akikazu Tanimoto, SPIE, Vol. 1088 Optical Laser Microlithography 2 (1989)" or Japanese Patent Laid-Open No. 57(1982)-198631.
A theoretical analysis of partial coherent imaging is introduced in "Stepper's Optics (1), (2), (3) and (4)" (Optical Technical Contact: Vol. 27, No. 12, pp. 762-771, Vol. 28, No. 1, pp. 59-67, Col. 28, No. 2, pp. 108-119, Vol. 28, No. 3, pp. 165-175).
Also, Japanese Patent Unexamined Publication No. 3-27516 describes an example in which a spatial filter is used to improve a resolving power.
Further, a phase shifter method for modifying a mask to improve a resolving power is known from Japanese Patent Publication No. 62(1987)-50811. According to this phase shifter method, light from a neighboring pattern is made to interfere, thereby enhancing the resolving power, which is realized by providing a film (a phase shifter) with phases alternately deviated through .pi. so that phases of adjacent patterns are inverted. However, the prior art known from the aforementioned Patent Publication No. 62(1987)-50811 has a problem in that an arrangement of the phase shifter is difficult, and the manufacture of a mask provided with the phase shifter is difficult.